1. Field of the Invention
The present invention relates generally to an automobile height control system which regulates the height position of a vehicle body relative to a road surface. More specifically, the invention relates to an automobile height control system which facilitates height adjustment at each of an automobiles suspension assemblys independently of the others. Further particularly, the invention relates to an automobile height control system which can regulate not only a vehicle's height but also a vehicle's attitude or inclination for improving driving stability, riding comfort and appearance.
2. Description of the Background Art
In recent years, there have been developed a plurality of automobile height control systems for facilitating better driving performance, riding comfort and appearance. The height control systems are generally designed for adjusting attitude or inclination of vehicle bodies relative to road surface. For example, one of the typical type of vehicular height control systems has been disclosed in "GALANT ETERNA.SIGMA.NEW MODEL EXPLANATION", page 111 through 137, published by Mitsubishi Motor Industries Co., Ltd., on August, 1983.
Such conventional vehicle height control systems employ a plurality of vehicle height sensors to monitor position of the associated section of the vehicle body relative to the road surface. The output of the height sensor is compared with reference value which defines a target vehicle height range. When the height is greater than the target height range, pressurized air in a pneumatic chamber in suspension assemblies is ventilated to reduce the pressure in the pnuematic chamber for decreasing the vehicle height toward the target height range. On the other hand, when the vehicle height is lower than the target height range, the pressure in the pneumatic chamber is increased to raise the vehicle height toward the target height range.
In the aforementioned height control system, the height adjustment is performed relative to respective sections of the vehicle body, where the height sensors are arranged. This facilitates control of the height at respective suspension assemblies, independently of the others. Such control systems successfully adjusts the height at respective positions of the vehicle body, it may not regulate the attitude of the vehicle. However, in practice, since there is a difference between the upper and lower limits of the target height range, this may adversely effect the inclination of the vehicle. For example, if one section of the vehicle is at the upper limit of the target height range and another section of the vehicle is at the lower limit of the target height range the vehicle could become inclined at an angle that would be detrimental to comfort appearance and performance characteristics of the vehicle.